Method of producing copper surfaces for improved bonding, compositions used therein and articles made therefrom

ABSTRACT

This invention relates to a method of forming a substrate with preparing a surface capable of making a cocontinuous bond comprising the steps of 1) obtaining a copper or copper alloy substrate and 2) applying an etching composition which comprises (a) an acid, (b) an oxidizing agent, (c) a copper complexing agent, and (d) a copper complex, wherein the copper complex is present in an amount which precipitates when applied to the copper or copper alloy substrate. The method also includes the step of 3) treating the substrate with a coating composition and/or 4) applying a stripping composition to the substrate. The invention also relates to copper articles, having surface porosity, including multilayer articles such as printed circuit boards and compositions used in the method. The present invention provides microporous copper or copper alloy substrates which have improved adhesion properties to organic material.

FIELD OF THE INVENTION

This invention relates to copper articles with a surface capable offorming a cocontinuous bond, and methods and compositions of making thesame.

BACKGROUND OF THE INVENTION

It is an ongoing problem to bond organic materials to metal surfaces.When the bond between the metal surface and the organic material isexposed to heat delamination may occur. Delamination is the separationof the organic material which was bonded to the metal surface.Multilayer printed circuit boards (PCB's) are typically constructed byinterleaving imaged conductive layers, such as one containing copperwith non-conductive layers such as a partially cured B-stage resin,i.e., a prepreg, into a multilayer sandwich which is then bondedtogether by applying heat and pressure. The conductive layer, e.g.,copper circuitry, does not bond well to the non-conductive B-stage resinprepreg. Often intermediate layers are used to bond the B-stage prepregto the copper circuitry.

To improve bonding, metal surfaces have been physically roughened toprovide increased surface area for bonding. Also, the metal surfaceshave been treated with chemicals to roughen the metal surface andimprove adhesion. Metal oxide layers, such as immersion coatings of tin,have been placed on the surface of the metal to improve adhesion.

WO 9619097 relates to metal surfaces, usually copper, which are micro-roughened to improve adhesion of polymeric materials. The metalsurfaces, usually copper, which are micro-roughened by use of anadhesion promoting composition comprising hydrogen peroxide, aninorganic acid, a corrosion inhibitor, such as a triazole, tettrazole,or imidazole.

SUMMARY OF THE INVENTION

This invention relates to a method of preparing a surface capable ofmaking a cocontinuous bond comprising the steps of 1) obtaining a copperor copper alloy substrate and 2) applying an etching composition whichcomprises (a) an acid, (b) an oxidizing agent, (c) a copper complexingagent, and (d) a copper complex, wherein the copper complex is presentin an amount which precipitates when applied to the copper or copperalloy substrate. The method also includes the step of 3) treating thesubstrate with a coating composition and/or 4) applying a strippingcomposition to the substrate. The invention also relates to copperarticles, having surface with interconnected channels capable of forminga cocontinuous bond including multilayer articles such as printedcircuit boards and compositions used in the method. The presentinvention provides a copper or copper alloy substrates which haveimproved adhesion properties to organic material.

DESCRIPTION OF THE FIGURES

FIG. 1 is a scanning electron photomicrograph of a microporous surface(magnification factor of 20,000×) prepared by the method of the currentinvention.

FIG. 2 is a scanning electron photomicrograph of an untreatedconventional copper surface (surface magnification factor of 5,000×).

FIGS. 3 and 4 are scanning electron photomicrographs (surfacemagnification factor of 5,000×) which illustrate the surface structuresachieved by the methods of the invention.

FIG. 5 is a scanning electron photomicrograph of an untreated vendormodified drum side treated copper surface, also called reverse treat(surface magnification factor of 5,000×).

FIGS. 6-7 are scanning electron photomicrograph of a drum side treatedcopper surface which has been prepared by the method of the currentinvention (surface magnification factor of 5,000×).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term cocontinuous bond refers to the structure which results whenthe treated copper surface is bonded to an organic material. Theresulting structure is cocontinuous because neither the organic materialnor the copper surface are discontinuous. The treated copper surface hasinterconnected channels and depressions. The organic material then flowsinto the channels and depressions. In the resulting bond, neither thecopper surface nor the organic material are discontinuous. The term isalso described in relation to polymer networks in U.S. Pat. No.5,266,610.

The passages of the interconnected channels have a diameter which istypically an average of less than about 20, or less than about 15, orless than about 10 microns. Preferably from about 50% to about 100% ofthe passages have an average diameter from about 1 to about 8 microns.The surface structure, e.g., the channels or depressions occur to adepth up to about 75, generally from about 1 to about 65, or from about5 to about 50 microns. Here as well elsewhere in the specification andclaims, the range and ratio limits may be combined. The channels and/ordepressions may form several layers with multiple application of theetching compositions. Each layer is prepared with each successivetreatment of the etching composition. Generally, the copper or copperalloy substrate has from one to about ten, or from about two to aboutnine, or from about three to about eight layers. The surface structureforms an open cellular network.

As described above, the present invention relates to a method ofproducing copper substrates with improved bonding. The substrate may bea copper or copper alloy substrate. The copper or copper alloy may be asolid block or foil supported on a dielectric substrate. The foils arethose know to those in the art.

The organic materials may be any organic materials which may be boundedto metal substrates. For instance, the organic material may be Teflon ororganic prepregs, organic adhesives, natural or synthetic elastomers, orinsulating materials for making printed circuit boards. The prepregsinclude FR-4, FR-10, G-10, polyimide, bis-maleimide triazine resin,polyvinyl fluorides and cyanate esters, and are known to those in theart.

The method for preparing the micropores, involves applying an etchingcomposition to a copper or copper alloy substrate. The etchingcomposition contains (a) an acid, (b) an oxidizing agent, (c) a coppercomplexing agent, and (d) a copper complex.

Acid

The acid may be any acid or mixture of acids which is strong enough toetch the copper or copper alloy in the presence of the other ingredientsof the etching composition to form micropores. The amount of acidcontained in the etching composition may vary from about 2% to about75%, or from about 4% to about 58%, or from about 5% to about 20% byweight. In another embodiment, the acid is present in an amount fromabout 20 to about 400, or from about 80 to about 200 grams of acid perliter of solution. Sufficient acid is present in the etching compositionto provide a pH from 0 to about 5, or from 0 to about 3, more often from0 to about 2. Generally, it is desirable to use an acid that has ananion common to the acid salts of the metals.

The acid is usually a mineral acid, alkane sulfonic acid, alkanolsulfonic acid, or mixtures thereof. Example of useful mineral acidsinclude sulfuric acid, perchloric acid, hydrochloric acid, fluoroboricacid, phosphoric acid, etc.

The alkane sulfonic acids may be represented by the following formula,R—SO₃H, wherein R is an alkyl group containing from about 1 to about 18,or from about 1 to about 12 carbon atoms. Examples of alkane sulfonicacids include, for example, methane sulfonic acid, ethane sulfonic acid,propane sulfonic acid, butane sulfonic acid, pentane sulfonic acid,hexane sulfonic acid, decane sulfonic acid and dodecane sulfonic acid.

The alkanol sulfonic acids may be represented by the following formula:(C_(n)H_(2n+1))—CH(OH)—(CH₂)_(m)—SO₃H wherein n is from 0 to about 10, mis from 1 to about 11 and the sum of m+n is from 1 up to about 12. Thehydroxy group of the alkanol sulfonic acids may be a terminal orinternal hydroxy group. Examples of useful alkanol sulfonic acidsinclude hydroxyethyl sulfonic acid, hydroxypropyl sulfonic acid,hydroxybutyl sulfonic acid, hydroxypentyl sulfonic acid, hydroxyhexylsulfonic acid, and hydroxydodecyl sulfonic acid.

The alkane sulfonic acids and alkanol sulfonic acids are availablecommercially and can also be prepared by a variety of methods known inthe art. One method comprises the catalytic oxidation of mercaptans oraliphatic sulfides having the formula R₁S_(n)R₂ wherein R₁ or R₂ arealkyl groups having from 1 to about 18 carbon atoms and n is a positiveinteger between 1 and 6. The metal salts of such acids are prepared, forexample, by dissolving a metal oxide in a hot concentrated aqueoussolution of an alkane or alkanol sulfonic acid.

Oxidizing Agent

The second component of the etching composition is an oxidizing agent.The oxidizing agent is generally present in an amount sufficient topromote formation of above described surface structure. Typically theoxidizing agent is present in an amount from about 0.0001% up to about10%, or from about 0.01% up to about 5%, or from about 0.1% up to about2% by weight. The dissolved air and oxygen are present in an amount topromote formation of the above described surface structure. Theoxidizing agents include dissolved air, oxygen, peroxides, persulfates,peroxysulfates, permanganates, chromic acid, soluble metal ions fromGroups IIIB, IVB, VB, and mixtures of two or more oxidizing agents. Theperoxides may be hydroperoxides and/or di-organo peroxides. Theperoxides include hydrogen peroxide and organic peroxides. The preferredorganic peroxides are those having organic groups, e.g., alkyl or arylgroups, containing from two to about twenty, preferably from about twoto about twelve carbon atoms. Examples of organic peroxides includetert-butyl peroxide, tert-amyl peroxide, benzoyl peroxide, etc.

The oxidizing agent may be a metal from Groups IIIB, IVB, and/or VB.Examples of these metal include tin, lead, bismuth, gallium and indium.The metal is in the form of a solution soluble salt such as a salt ofthe acids or complexing agents above.

Complexing Agent

Along with the acid and the oxidizing agent, the etching compositioncontains a copper complexing agent. The amount of complexing agentsincluded in the etching compositions is from about 0.5% to about 20%, orfrom about 1% to about 15%, or from about 2% to about 10% by weight.When the solubility of the complexing agent is low, a cosolvent may beadded to solubilize the complexing agent and thereby enhance itsactivity in the resulting solution. Suitable cosolvents includewater-miscible solvents such as alcohols (e.g., ethanol), glycols (e.g.,ethylene glycol), alkoxy alkanols (2-butoxy ethanol), ketones (e.g.,acetone), aprotic solvents (e.g., dimethylformamide, dimethylsulfoxide,acetonitrile, etc.), etc.

The copper complexing agent include ureas, including thioureas, ioimidazole-thiones, and mixtures thereof and derivatives, homologs, andanalogs thereof. Specific examples of copper complexing agents includeurea nitrate, urea oxalate, 1-acetylurea, 1-benzylurea, 1-butylurea,1,1-diethylurea, 1,1-diphenylurea, 1 -hydroxyurea, thiourea, etc.Examples of useful urea derivatives are found in Holtzman et al, U.S.Pat. No. 4,657,632, which is incorporated herein by reference.

The imidazole-thiones include imidazole-2-thione which is represented bythe formula compound

wherein A and B are the same or different —RY groups wherein R is alinear, branched or cyclic hydrocarbylene group containing up to 12carbon atoms, and Y is a hydrogen, halogen, cyano, vinyl, phenyl, orether moiety.

In one embodiment, the complexing agent is a1,3-dialkylimidazole-2-thione compound (where A and B are eachindividually alkyl or cycloalkyl groups), and the thione compound may beunsymmetrical (A and B are different) or symmetrical (A and B are thesame). Preferably, the complexing agents are unsymmetrical such as(where A is methyl or ethyl and B is an alkyl or cycloalkyl groupcontaining from 3 to 6 carbon atoms). Preferably, when A is methyl, B isa C₃-C₆ alkyl or cycloalkyl group, and when A is ethyl, B is a C₄-C₆alkyl or cycloalkyl group. An example of an unsymmetrical compound is1-methyl-3-propylimidazole-2-thione.

Alternatively, symmetrical 1,3-dialkylimidazole-2-thione compounds maybe used and the dialkyl groups are the same alkyl or cycloalkyl groupscontaining from 1 to 6 carbon atoms. An example of this class ofcomplexing agents is 1,3-dimethylimidazole-2-thione.

The imidiazole-2-thione complexing agents are described in U.S. Pat. No.5,554,211, issued to Bokisa et al. This patent is incorporated for itsdisclosure of the thione as well as immersion metal compositions andmethods.

Copper Complex

The etching compositions also include a copper complex. The coppercomplex is present in an amount sufficient to precipitate when appliedto the copper or copper alloy substrate. The copper complex, generallyis present in an amount from about 5 grams per liter up to thesolubility limit of the copper complex. The amount of copper isexpressed as grams per liter or g/l. It is understood here andthroughout the specification that the term refers to the amount of metalper liter. For instance, the amount of complexing agent is at leastabout 5 g/l as copper metal. In one embodiment, the copper complex ispresent in an amount from about 5 up to about 75, or from about 15 toabout 60 or from about 20 to about 40 grams per liter as copper. Thecopper complex includes copper complexes of the above-identifiedcomplexing agents or a combination of the above complexing agents withone of the above acids. In a preferred embodiment, the copper complex isa copper thiourea or a copper imidiazole-2-thione.

The etching composition may include one or more surfactants compatiblewith each of the metal salts, the acids and the complexing agent. Theetching composition may optionally contain at least one surfactant in aconcentration from about 0.01 to about 100 grams per liter of bath andmore preferably from about 0.05 to about 20 grams per liter of bath. Thesurfactant may be at least one surfactant including amphoteric,nonionic, cationic, or anionic surfactants; or mixtures thereof. Moreoften, the surfactant is at least one cationic or anionic surfactant; ormixtures thereof. The nonionic surfactants are preferred.

A variety of nonionic surfactants include the condensation products ofethylene oxide and/or propylene oxide with compounds containing ahydroxy, mercapto or amino group. Examples of materials containinghydroxyl groups include alkyl phenols, styrenated phenols, fattyalcohols, fatty acids, polyalkylene glycols, etc. Examples of materialscontaining amino groups include alkylamines and polyamines, fatty acidamides, etc.

Examples of nonionic surfactants include ether containing surfactantswhich may be produced by treating fatty alcohols or alkyl or alkoxysubstituted phenols or naphthols with excess ethylene oxide or propyleneoxide. The alkyl group may contain from about 14 to about 24 carbonatoms and may be derived from a long chain fatty alcohol, such as oleylalcohol or stearyl alcohol.

Nonionic polyoxyethylene compounds are described in U.S. Pat. No.3,855,085, which is incorporated by reference. Polyoxyethylene compoundsare available commercially under the general trade designations“Surfynol” by Air Products and Chemicals, Inc. of Wayne, Pa., under thedesignation “Pluronic” or “Tetronic” by BASF Wyandotte Corp. ofWyandotte, Mich., and under the designation “Surfonic” by HuntsmernCorporation of Houston, Tex.

Alkoxylated amine, long chain fatty amine, long chain fatty acid,alkanol amines, diamines, amides, alkanol amides and polyglycol typesurfactants known in the art are also useful. One type of amine usefulsurfactant is the group of surfactants obtained by the addition of amixture of propylene oxide and ethylene oxide to diamines. Morespecifically, compounds formed by the addition of propylene oxide toethylene diamine followed by the addition of ethylene oxide are usefuland are available commercially from BASF Wyandotte, Ind. Chemical Groupunder the general trade designation “Tetronic”.

Carbowax-type surfactants, which are polyethylene glycols havingdifferent molecular weights, also are useful. Other known nonionicglycol derivatives, such as polyalkylene glycol ethers and methoxypolyethylene glycols, are available commercially and may be utilized assurfactants.

Ethylene oxide condensation products with fatty acids also are usefulnonionic surfactants. Many of these are available commercially under thegeneral tradename “Ethofat” from Armak Ind. Examples of thesesurfactants include condensates of coco acids, oleic acid, etc. Ethyleneoxide condensates of fatty acid amides, e.g., oleamide, also areavailable from Armak Ind.

Polyoxyalkylated glycols, phenols and/or naphthols may also be included.Many of these condensates are available commercially under such tradenames as “Tween” from ICI America, “Triton” from Rohm & Haas Co.,“Tergitol” from Union Carbide, and “Igepal” from General Aniline andFilm Corp.

The surfactants utilized in the etching compositions also may beamphoteric surfactants. The preferred amphoteric surfactants includebetaines and sulfobetaines, and sulfated or sulfonated adducts of thecondensation products of ethylene oxide and/or propylene oxide with analkyl amine or diamine. Examples of these surfactants includelauryidimethylammonium betaine, stearyl dimethylammonium betaine, asulfated adduct of an ethoxylated alkylamine, Triton QS-15 (Rohm & HaasCo.), a sodium salt of a sulfonated lauric derivative, Miranol HS, and asodium salt of a sulfonated oleic acid, Miranol OS.

Cationic surfactants also are useful in the etching compositions and maybe selected from higher alkyl amine salts, quaternary ammonium salts,alkyl pyridinium salts and alkyl imidazolium salts. Examples of theabove described cationic surfactants, in the form of salts, arelauryltrimethylammonium salt, stearyltrimethylammonium salt,octadecyidimethylethylammonium salt, dimethylbenzyllaurylammonium salt,octadecyidimethylbenzylammonium salt, triethylbenzylammonium salt,laurylpyridinium salt, dodecylpicolinium salt,1-hydroxyethyl-1-benzyl-2-laurylimidazolinium salt,1-hydroxyethyl-1-benzyl-2-oleylimidazolinium salt, stearylamine acetate,laurylamine acetate, and octadecylamine acetate.

Cationic surfactants obtained by condensation of various amounts ofethylene oxide or propylene oxide with primary fatty amines are usefuland are prepared by condensing various amounts of ethylene oxide withprimary fatty amines which may be a single amine or a mixture of aminessuch as are obtained by the hydrolysis of tallow oils, sperm oils,coconut oils, etc. Specific examples of fatty acid amines containingfrom 8 to 30 carbon atoms include saturated, as well as unsaturated,aliphatic amines such as octyl amine, decyl amine, lauryl amine, stearylamine, oleyl amine, myristyl amine, palmityl amine, dodecyl amine, andoctadecyl amine. Alkoxylated amines, e.g., coconut fatty amine, stearylamine, and tallow amine, are available from the Armak Chemical Divisionof Akzona, Inc., Chicago, Ill., under the general trade designation“Ethomeen”. Specific examples of such products include “Ethomeen C/15”“Ethomeen C/20”, “C/25”, “Ethomeen S/15” and “S/20” and “Ethomeen T/15”and “T/25”. Commercially available examples of the alkoxylated diaminesinclude “Ethoduomeen T/13” and “T/20” which are ethylene oxidecondensation products of N-tallow trimethylene diamine containing about3 and 10 moles of ethylene oxide per mole of diamine respectively.

The amine ethoxylate surfactants exhibit the characteristics of bothcationic and nonionic surfactants with the nonionic propertiesincreasing at the higher levels of ethoxylation. That is, as the levelof ethoxylation increases, the ethoxylated amine behaves more like anonionic surfactant. Useful surfactants are available commercially suchas from Texaco Chemical Company under the trade designation “M-300Series”, such as M-302, M-305, M-31 0, M-315 and M-320 which contain atotal to 2, 5, 10, 15 and 20 moles of ethylene oxide respectively.

The surfactants also may be anionic surfactants. Examples of usefulanionic surfactants include sulfated alkyl alcohols, sulfated lowerethoxylated alkyl alcohols, and their salts such as alkali metal salts.Examples of such surfactants include sodium lauryl sulfate (Duponol C orQC from DuPont), sodium mixed long chain alcohol sulfates available fromDuPont under the designation Duponol WN, sodium octyl sulfate availablefrom Alcolac, Ltd. under the designation Sipex OLS, Sodium tridecylether sulfate (Sipex EST), sodium lauryl ether sulfate (Sipon ES),magnesium lauryl sulfate (Sipon LM), the ammonium salt of lauryl sulfate(Sipon L-22), diethanolamino lauryl sulfate (Sipon LD), sodiumdodecylbenzene sulfonate (Siponate DS), etc.

The etching compositions may also contain one or more chelating agents.The chelating agents generally comprise the various classes of chelatingagents and specific compounds disclosed in Kirk-Othmer, Encyclopedia ofChemical Technology, Third Edition, Vol. 5, pp. 339-368. This disclosureis hereby incorporated by reference. Chelating agents that areespecially preferred comprise polyamines, aminocarboxylic acids andhydroxy carboxylic acids. Some aminocarboxylic acids that may be usedcomprise ethylenediaminetetraacetic acid,hydroxyethylethylenediaminetriacetic acid, nitrilotriacetic acid,N-dihydroxyethylglycine, and ethylenebis(hydroxyphenylglycine). Hydroxycarboxylic acids that may be used comprise tartaric acid, citric acid,gluconic acid and 5-sulfosalicylic acid. Other useful chelating agentsinclude polyamines such as ethylenediamine, dimethylglyoxime,diethylenetriamine, etc.

Various reducing agents that may be included in the etchingcompositions, and these generally comprise organic aldehydes whethersaturated or unsaturated, aliphatic or cyclic, having up to about 10carbon atoms. Glucose has been found to prevent oxidation of the metalsalts to a higher oxidation state, e.g., tin (II) ion to tin (IV) ion,but also as a chelating agent and is especially useful for thesereasons. Other useful reducing agents include hypophosphorous acid,dimethylamino borane, etc.

Method

The present method involves the formation of a copper or copper alloysubstrate capable of forming a cocontinuous bond by an etchingcomposition. The application of the composition may be accomplished byimmersion of the substrate or spraying the etching composition on thesubstrate. Single jet, fan or cone nozzles may be used in the sprayapplication. The immersion method of applying the etching composition isgenerally in an aerated or agitated dip tank. Additionally, fluid headmethods and ram jet methods may be used to apply the etching compositionas is known to those in the art. The time of spraying is long enough forthe formation of the above described surface structure. Generally, thespraying is accomplished in about 0.1 to about 5, or from about 0.25 toabout 3, or from about 0.5 to about 2 minutes.

Generally speaking, the etching composition is maintained at atemperature higher than the temperature of the substrate. In oneembodiment, the etching composition is maintained at a temperature fromabout 40° F. to 150° F., or from about 60° F. to 130° F., or from 80° F.to about 120° F. When the copper complex which is in a warm compositionis applied to a cooler substrate, the copper complex precipitates.

The copper or copper alloy substrate with the above described surfacestructure may be used in a variety of applications where improvedbonding between organic materials and copper or copper alloy surfacesare desired. For instance, the substrate may be (1) treated with a metalcoating composition, a silane coating composition, and/or a metalstripping composition, (2) treated with vulcanizable adhesive, (3)treated with photoimageable, coating element, (4) treated to form acopper oxide coating, and (5) treated to form a reduced copper oxidecoating. The copper or copper alloy substrate may also be metal used inpreparation of tires, reinforced tubing or other metal reinforced rubberproducts. The metal reinforcement may be the copper or copper alloysubstrate. The copper or copper alloy substrate may be a coating onother metals used in metal reinforced rubber products. The copper orcopper alloy substrate may be infiltrated with ceramic material to forma cocontinuous structure and used where better ceramic and metal bondingis desired. The copper or copper alloy substrate may also be used inimproved bonding in brake pads.

Metal Coating Composition

In one embodiment, the method involves the step of treating thesubstrate with a metal coating composition, e.g., an electroless metalcoating composition. The metal coating composition is typically animmersion metal coating composition. The metal coating compositions arethose used to form metal oxide/hydroxide layers on copper or copperalloys. The metal coating composition comprises (1) at least onesolution soluble metal salt, (2) an acid, such as those disclosed above,(3) a complexing agent, such as those disclosed above, and (4) water.The metals of the metal coating composition include bismuth, galium,germanium, gold, indium, lead, palladium, silver, tin and alloys ofthese metals.

The metal coating composition generally contains from about 1 to 100, orfrom about 2 to about 50, or from about 5 to about 30 g/l of metal asthe metal salt. The acid is present in an amount from about 1% to about30%, or from about 5% to about 20% by weight. The amount of complexingagent included in the metal coating compositions may range from about 5grams per liter up to the solubility limit of the complexing agent inthe plating solution. Generally, the coating composition will containfrom about 5 to about 100 grams of complexing agent per liter, and moreoften from about 40 to about 80 grams per liter. When the solubility ofthe complexing agent is low, a cosolvent may be used as discussed above.

The metal coating compositions also may contain one or more of the abovesurfactants, chelating agents or reducing agents disclosed above.

The metal coating compositions are described in U.S. Pat. Nos.4,715,894, and 4,882,202 issued to Holtzman et al, U.S. Pat. No.4,871,429, issued to Nobel et al, U.S. Pat. No. 5,073,456, issued toPalladino, and U.S. Pat. No. 5,554,211, issued to Bokisa et al. Thesepatents are incorporated by reference for their disclosure of metalcoatings and methods of using the same.

Silane Coating

In another embodiment of the present invention, the copper or copperalloy substrate having the above described surface structure may betreated with a silane coating composition. The silane coatingcomposition may be (a) applied directly to the copper or copper alloysubstrate or (b) applied to the metal oxide/hydroxide layer on thecopper or copper alloy substrate formed from the metal coatingcomposition, i.e. the immersion metal coating, described above. Anorganosilane composition is used to bond the metal oxide, metalhydroxide, or combination thereof to one or more insulating layers. Theorganosilane may be placed on the metal oxide, metal hydroxide orcombination thereof or an insulating layer.

The silane coating composition comprises a mixture of (i) at least onesilane coupling agent and (ii) at least one member selected from thegroup consisting of a tris(silylorgano) amine, atris(silylorgano)alkane, a disysyl compound and a non-epoxy hydrolyzablesilane containing a heterocyclic, acryloxy, amide, or carbon-carbondouble bond containing group. In one embodiment, the organosilanecompositions comprise (i) a mixture of at least one silane couplingagent and (ii) a tris(silylorgano)amine or alkane, as described below.In another embodiment, the organosilane composition comprises (i) amixture of an ureido silane and (ii) a disylyl compound, as describedhereinafter.

Silane coupling agents are well known, and various conventional silanecoupling agents may be utilized. Examples of silane coupling agentsinclude silane esters, amino silanes, amido silanes, ureido silanes,halo silanes, epoxy silanes, vinyl silanes, methacryloxy silanes,mercapto silanes, and isocyanato silanes. The alkyl and aryl groups maycontain up to about 10 carbon atoms. Alkyl groups containing from 1 toabout 5 carbon atoms are particularly useful. In one embodiment, n is aninteger from 0 to 10 and more often from 1 to about 5.

Specific examples of silane coupling agents useful in the firstembodiment of the present invention includeN-(2-aminoethyl)-3-aminopropyltrimethoxysilane,3-methacryloxypropyltrimethoxysilane,3-(2-(vinylbenzylamino)ethylamino)-propyltrimethoxysilane,3-glycidoxypropyltrimethoxysilane, triacetoxyvinylsilane,tris-(2-methoxyethoxy)-vinylsilane, 3-chloropropyltrimethoxysilane, 1-trimethoxysilyl-2-(p,m-chloromethyl)phenylethane,3-chloropropyltriethoxysilane,N-(aminoethylaminomethyl)phenyltrimethoxysilane,N-(2-aminoethyl)-3-aminopropyl tris(2-ethylhexoxy)silane,3-aminopropyltrimethoxysilane, trimethoxysilylpropylenetriamine,β(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-mercaptopropyltrimethoxysilane, 3-mercaptotriethoxysilane,3-mercaptopropylmethyidimethoxysilane,bis(2-hydroxyethyl)-3-aminopropyltrimethoxysilane,1,3-divinyltetramethyldisilazane, vinyltrimethoxysilane,2-(diphenylphosphino)ethyltriethoxysilane,2-methacryloxyethyidimethyl[3-trimethoxysilylpropyl]ammonium chloride,3-isocyanatopropyidimethylethoxysilane,N-(3-acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane, vinyltris(t-butylperoxy)silane, methyltrimethoxysilane,ethyltrimethoxysilane, phenyltrimethoxysilane, phenyltriacetoxysilane,methyltrimethoxysilane, phenyltrimethoxysilane.

The preferred silane coupling agents are those which are commerciallyavailable and which are recognized by those skilled in the art as beingeffective coupling agents. A number of organofunctional silanes areavailable, for example, from Union Carbide, Specialty ChemicalsDivision, Danbury, Connecticut. Examples of useful silane couplingagents available from Union Carbide are summarized in the followingtable.

TABLE I Silane Coupling Agents Trade Type Designation Formula EstersA-137 (EtO)₃SiC₈H₁₇ A-162 (EtO)₃SiCH₃ Amino A-1100 (EtO)₃Si(CH₂)₃NH₂A-1110 (MeO)₃Si(CH₂)₃NH₂ A-1120 (MeO)₃Si(CH₂)₃NH(CH₂)₂NH₂ A-1130(MeO)₃Si(CH₂)₃NH(CH₂)₂NH(CH₂)₂NH₂ Ureido A-1160* (EtO)₃Si(CH₂)₃NHC(O)NH₂Isocyanato A-1310 (EtO)₃Si(CH₂)₃N═C═O Vinyl A-151 (EtO)₃SiCH═CH₂ A-171(MeO)₃SiCH ═CH₂ A-172 (CH₃OC₂H₄O)₃SiCH═CH₂ Methacryloxy A-174(MeO)₃Si(CH₂)₃OC(O)C(CH₃)═CH₂ Epoxy A-187

Mercapto A-189 (MeO)₃Si(CH₂)₃SH *50% w/w in methanol

In one embodiment, the silane coupling agent is a ureido silanerepresented by the formula

B_((4−n))—Si—(A—N(H)—C(O)—NH₂)_(n)

wherein A is an alkylene group containing from 1 to about 8 carbonatoms, B is a hydroxy or alkoxy group containing from 1 to about 8carbon atoms and n is an integer from 1 to 3 provided that if n is 1 or2, each B may be the same or different. In one embodiment, each B is analkoxy group containing 1 to about 5 carbon atoms, particularlymethyloxy or ethyloxy groups, and A is a divalent hydrocarbyl groupcontaining from 1 to about 5 carbon atoms. Examples of such divalenthydrocarbyl groups include methylene, ethylene, propylene, butylene,etc. Specific examples of such ureido silanes includeβ-ureidoethyl-trimethoxysilane; β-ureidoethyl-triethoxysilane;γ-ureidoethyl-trimethoxysilane; γ-ureidopropyl-triethoxysilane, etc.

The second component in the organosilane compositions useful in thepresent invention is (1) a tris(silylorgano)amine characterized by theformula

((R⁵O)₃Si—R⁶—)₃—N

or (2) a tris(silylorgano)alkane characterized by the formula

((R⁵O)₃Si—R⁶—)₃—C—R⁷

or, (3) a disylyl compound of the formula

(R⁵O)₃—Si—R⁶—Si—(OR⁵)₃

wherein each R⁵ is independently an alkyl, alkoxyalkyl, aryl, aralkyl orcycloalkyl group of less than 20 carbon atoms; R⁶ is a divalenthydrocarbon or polyether group of less than 20 carbon atoms; and R⁷ is afunctional group represented by C_(n)H_(2n)X, wherein n is from 0 to 20,and X is selected from the group consisting of amino, amido, hydroxy,alkoxy, halo, mercapto, carboxy, acyl, vinyl, allyl, styryl, epoxy,isocyanato, glycidoxy, and acryloxy groups. In one embodiment, each R⁵group is independently an alkyl, alkoxy alkyl, aryl, aralkyl orcycloalkyl group of less than 10 carbon atoms and is more often an alkylgroup containing from 1 to 5 carbon atoms or an alkoxy alkyl groupcontaining from 2 to 10 carbon atoms. R⁶ is a divalent hydrocarbon ordivalent polyether group containing less than 20, or up to about 8carbon atoms. R⁶ can be, for example, alkylene groups such as methylene,ethylene, propylene, ethylidene and isopropylidene; cycloalkylenes suchas cycloheptylene and cyclohexylene; divalent aromatic groups such asphenylene, tolylene, xylylene, and naphthalene; and divalent groups ofaralkanes of the formula, —C₆H₄—R′—, wherein R′ is an alkylene groupsuch as methylene, ethylene or propylene. R⁶ also can be, for example, adivalent polyether of the formula —R⁸—(O—R⁸)_(z)—, wherein R⁸ is analkylene group and z is an integer of from 1 to about 5. The divalentpolyether group can be, for example, diethylene ether. In oneembodiment, R⁷ is defined the same as Group B above, where group B is afunctional group.

The tris (silylorgano)amines which are useful in the silane compositionsare known compounds, and procedures for preparing such tris(silylorgano)amines have been described in, for example, U.S. Pat. Nos.5,101,055; 2,920,095; and 2,832,754; and the disclosures of thesepatents with regard to the tris (silylorgano)amines and methods forpreparing such amines are hereby incorporated by reference.

Specific examples of tris(silylorgano)amines which are useful in thesilane compositions include tris (trimethoxysilylmethyl)amine; tris(triethoxysilylmethyl)amine; tris (trimethoxysilylethyl)amine; tris(trimethoxysilylethyl)amine; tris (trimethoxysilylethyl)amine; tris(triethoxysilylpropyl)amine; tris (dimethoxyethoxysilylpropyl)amine;tris(tripropoxysilylpropyl)amine; etc.

As described in U.S. Pat. No. 5,101,055, the tris (silylorgano)aminesmay be prepared from the corresponding bis-amine by contacting thebis-amine with particulate palladium monoxide at a temperature withinthe range of from about 50° C. to 300° C. Another procedure forpreparing the tris (silylorgano)amine compounds utilizes the reaction ofthe bis (trialkoxysilylalkyl)amine with an equimolar amount of atrialkylsilyipropyl halide, such as the chloride. For example, tris(trimethoxysilylpropyl)amine can be prepared by reacting bis(trimethoxysilylpropyl)amine with trimethoxysilylpropyl chloride. Thisprocess is a modification of the process described in U.S. Pat. No.4,775,415 used for preparing bis (trimethoxysilylpropyl)amine from3-aminopropyltrimethoxysilane and 3-chloro propyltrimethoxy silane.

In another embodiment, the silane composition includes a disylylcompound, such as those represented by the above formula.

(R⁵O)₃—Si—R⁶—Si—(OR⁵)₃

wherein R⁵ and R⁶ are defined above. Examples of these materials includebis (trimethoxysilyl) ethane, bis (triethoxysilyl) ethane, hexamethoxydisilylethane, etc. The disylyl compounds may be made by means known tothose in the art. For instance, the disylyl compounds may be prepared byreacting a chloroalkyltrialkyoxysilane with a tetraalkoxysilane. U.S.Pat. No. 4,689,085, issued to Plueddemann, describes disylyl compoundsand methods of their preparation. This patent is incorporated byreference for such disclosure.

The amounts of the silane coupling agent (i) and the tris(silylorgano)amine or alkane or disylyl compound (ii) utilized in thesilane compositions may vary over a wide range. For example, the weightratio of the silane-coupling agent (i) to the tris (silylorgano)amine oralkane or disylyl compound (ii) may range from about 1:99 and about99:1. More often, the ratio, expressed as a mole ratio of (i):(ii), isin the range from about 1:1 to about 5:1.

In another embodiment, the silane compositions include a non-epoxy groupcontaining hydrolyzable silane possessing a heterocyclic, such as animidazole or pyrrole; acryloxy; amide; or carbon-carbon double bondcontaining group, such as styryl. These silanes are used in combinationwith one or more of the above described alkoxy, alkyl or epoxycontaining silanes. The non-epoxy group containing silane is representedby the formula

(Y—R)_(α)Si(X)_(4−α)  (I)

wherein a is 1 or 2, X is a hydrolyzable group, R is a hydrocarbon groupand Y is a functional group containing an activated double bond selectedfrom the group consisting of heterocyclic, acryloxy, amide and a carboncarbon double bond containing group, with the proviso that X and Y arenot epoxy-containing groups.

Hydrolyzable groups, which may contain from 1 to about 8 carbon atoms,preferably contain 1 to about 4 carbon atoms. Hydrolyzable groups alsoinclude halogens. For example, X includes hydrocarbyloxy and alkoxygroups, such as methoxy, ethoxy, propyloxy and butoxy groups, as well aschlorine, bromine, and iodine. Hydrocarbon groups include alkyl,alkenyl, or any other group substantially containing carbon and hydrogenatoms. In one embodiment, R is an alkyl group containing 1 to about 5carbon atoms. In another embodiment, R is an alkyl group containing 1 toabout 3 carbon atoms. In another embodiment, the silane is characterizedby the absence of free amino groups.

Y is a functional group which must be compatible with the curingmechanism of the prepreg resin. Y is therefore selected fromheterocyclic groups, acryloxy groups, amide groups and carbon carbondouble bond containing groups. Examples of heterocyclic groups includesubstituted and unsubstituted pyrroles, pyrazoles, imidazoles,pyrrolidines, pyridines, pyrimidines, oxazoles, thiazoles, furans,thiophenes. Preferably, nitrogen containing heterocyclic groups areused. Preferably, heterocyclic groups having some degree of unsaturationare used. Examples of acryloxy groups include acryloxy, alkylacryloxygroups such as methacryloxy, and the like. Examples of carbon carbondouble bond containing groups include alkenyl, cyclopentadienyl, styryland phenyl.

Examples of such silanes include N-(3-trimethoxysilylpropyl)pyrrole,N-[3-(triethoxysilyl)propyl]-4,5-dihydroimidazole,β-trimethoxysilylethyl-2-pyridine, N-phenylaminopropyltrimethoxysilane,3-(N-styrylmethyl-2-aminoethylamino)propyltrimethoxysilane,methacryloxypropenyltrimethoxysilane,3-methacryloxypropyl trimethoxysilane,3-methacryloxypropyl tris(methoxyethoxy)silane,3-cyclopentadienyl propyltriethoxysilane,7-oct-1-enyltrimethoxysilane, Prosil® 9214 from PCR, Inc. (a carboxyamide silane), and the like. Silanes such asN-[3-(triethoxysilyl)propyl]-4,5-dihydroimidazole and3-methacryloxypropyl trimethoxysilane are preferred. The non-epoxycontaining silane and their means of preparation are described in U.S.Pat. No. 5,614,324, which is incorporated by reference for thosedisclosures.

The silane compositions may comprise other materials such as solvents,fillers, etc. Solvents should be capable of solubilizing both the silanecoupling agent and the tris(silylorgano)amino or alkane or disylylcompound. Typically, such solvents include lower alcohols such asmethanol, butanol or isopropanol. Water, or mixtures of water andalcohols can also be used as a solvent, but the stability of suchsolutions is generally more limited than the solutions made withalcohols. Small portions of water can be added to the silanecompositions in order to hydrolyze the conventional silane couplingagent (A) and the tris(organosilyl)amine or alkane or disylyl compound.Alternatively, dispersions or emulsions of the silane compositions canbe prepared in suitable organic solvent or mixtures of water and organicsolvent. Typical solvents include, in addition to the alcohols describedabove, ethers, ketones, aliphatic and aromatic hydrocarbons, amides suchas N,N-dimethylformamide, etc. Aqueous emulsions of the silane-couplingagents can be prepared in the conventional manner using conventionaldispersants and surfactants, including nonionic surfactants. The solidscontent of the silane compositions may vary from 100% by weight in puremixtures to as little as 0.1 weight percent or less in very dilutesolutions or emulsions. More often, the solids content of solutions willbe between about 0.5% and about 5% by weight.

Metal Stripper

In another embodiment, the copper or copper alloy substrate is treatedwith a metal stripper. The metal stripper is applied by immersion orspraying, as discussed above. The metal stripper composition may beapplied to the copper or copper alloy substrate or the metaloxide/hydroxide layer formed from the metal coating composition. Themetal stripper is added in an amount to remove some of the coppercomplex which deposits upon treatment with the etching composition. Themetal stripper may be any combination useful in stripping metal as isknown to those in the art.

Examples of useful metal strippers are inhibited acid or cyanidesolutions. The acids include sulfuric and sulfonic acids and othermineral acids useful in metal stripping compositions. The cyanidestripper compositions include alkali or alkaline earth metal or ammoniumcyanide stripping compositions known to those in the art. The inhibitedcompositions typically are inhibited by nitrocompounds. Examples ofuseful inhibiting compounds include nitrobenzenes, nitrobenzoic acids,nitroanilines, nitrophenols, nitrosulfonic acids, nitrobenzaldehydes,nitroparafins and nitroalkanes. The metal stripping compositions areknown to those in the art and described in U.S. Pat. Nos. 2,649,361,2,698,781 and 2,937,940, the disclosures of which are incorporated byreference. Metal stripping compositions are available commercially.Examples of metal stripping compositions are Rostrip M-20 and M-50available commercially from McGean Rohco, Inc.

Vulcanizable adhesive

In another embodiment, the copper or copper alloy substrate with thesurface structure described herein is treated with a vulcanizableadhesive which is crosslinked by chemical bonding through sulfur atoms.The adhesive contains chemicals having a vulcanizable unsaturated bondand at least one type of vulcanizing agent selected from sulfur, anorganic sulfur donor and an organic thiol. The chemicals havingvulcanizable unsaturated bonds include monomer, oligomers, polymers orelastomers having vulcanizable unsaturated bonding such as unsaturatedrubbers, including styrene butadiene rubbers, nitrile butadiene rubbers,isoprene rubbers, fluorocarbon rubbers, butyl rubbers, and naturalrubbers; ethylene alpha-olefin copolymer elastomers prepared with adiene, including ethylene propylene diene terpolymers and ethylenebutene diene terpolymers; unsaturated polyester resins based on maleicanhydride, fumaric acid, itaconic acid and citraconic acids; unsaturatedepoxy acrylate resins; maleimides; etc. The vulcanizable rubber is curedwith the vulcanizing agent to improve adhesion to copper laminates. Theprocess, vulcanizable chemicals, vulcanizing agents, and additionalchemicals used in this process are described in U.S. Pat. No. 5,569,545,issued to Yokono et al, whose disclosure is hereby incorporated byreference.

Photoimageable Permanent Coating

In another embodiment, the copper or copper alloy substrate with thesurface structure described herein is treated with an aqueousprocessable, multilayer, photoimageable, permanent coating elementdescribed in U.S. Pat. No. 5,643,657, issued to Dueber et al. Thispatent is incorporated by reference for its disclosed of the coatingelements, and methods and ingredients for making the coating element.

The photoimageable coating element has two layers. The first layer of aphotoimageable permanent coating composition comprises: (i) anamphoteric binder; (ii) a carboxyl group containing copolymer binder ofthe formula

wherein R₁ is H or alkyl; R₂ is phenyl or —CO₂R₃; and R₃ is H or alkylwhich is unsubstituted or substituted with one or more hydroxy groups;(iii) a monomer component containing at least two ethylenicallyunsaturated groups; and (iv) a photoinitiator or photoinitiator system.

The second layer of a photoimageable permanent coating compositioncomprises: (i) a cobinder system comprising at least one low molecularweight copolymer binder component having a molecular weight of from3,000 to 15,000 and containing from 2% to 50% by weight of at least onecarboxylic acid containing structural unit and from 50% to 98% by weightof at least one structural unit of the formula

wherein R₄ is H, alkyl, phenyl or aryl; R. is H, CH₃, phenyl, aryl,—COOR₆, —CONR₇R₈ or —CN; and R₆, R₇ and R₈ independently are H, alkyl oraryl, which is unsubstituted or substituted with one or more hydroxy,ester, keto, ether or thioether groups; and at least one high molecularweight carboxylic acid containing copolymer binder component having amolecular weight of from 40,000 to 500,000 and containing structuralunits of the formula

wherein R₉ is H, alkyl, —CN, phenyl, alkyphenyl or aryl; R₁₀ is phenyl,alkylphenyl, aryl, —COOR₁₁ or —CONR₇R₈; R₁₁ is H or alkyl; and whereinalkyl contains from 1 to 8 carbon atoms; (ii) an acrylated urethanemonomeric component; (iii) a photoinitiator or a photoinitiator system;and (iv) a blocked polyisocyanate crosslinking agent.

Preferably, the first layer is applied by conventional means to thetemporary support film from a solution and then dried. The second layerof photoimageable permanent coating may be applied as a solution or apreformed layer to the exposed surface of the first layer byconventional means to obtain high adhesion between these two layers.

The first and second layers are developable with about the sameconcentration of aqueous alkaline solution, such as 1% sodium orpotassium carbonate in less than 5 minutes at 40° C., so that the entirethickness of the first and second layers can be washed away in a singledevelopment step to leave a resist image of both layers on the substratesurface.

The combined thickness of the photoimageable layers depends on therelief pattern on the surface of the circuit substrate. Generally, thetotal thickness will be no greater than 125 microns (5 mils). When thepermanent coating composition is used in vacuum or roll lamination, thetotal thickness will generally be no greater than 76 microns (3 mils).Normally, the first layer will comprise from 0.1 to 30%, preferably from1 to 10%, of the combined layer thickness.

The first layer of photoimageable permanent coating, preferably,contains from 5 to 25 parts by weight of amphoteric binder, from 30 to80 parts by weight of carboxyl containing copolymer binder, from 5 to 30parts by weight of an ethylenically unsaturated monomer; and from 0.5 to10 parts by weight of a photoinitiator or photoinitiator system.

The second layer of photoimageable permanent coating, preferably,contains from 20 to 80 parts by weight of a cobinder system comprising alow molecular weight copolymer component having carboxylic acidfunctionality and a high molecular weight carboxylic acid containingcopolymer, from 10 to 40 parts by weight of an acrylated urethanemonomer component; from 0.5 to 10 parts by weight of a photoinitiator orphotoinitiator system; and from 5 to 25 parts by weight of a blockedpolyisocyanate crosslinking agent.

The amphoteric polymers of the first layer of the photoimageablecompositions are copolymers derived from the copolymerization of (1) atleast one basic comonomer which is an acrylic or methacrylic acrylamideor methacrylamide, an aminoalkyl acrylate or methacrylate or mixture ofany of these; (2) at least one acidic comonomer containing one or morecarboxyl groups and (3) at least one further comonomer which is acrylicor methacrylic in character.

The acrylamide and methacrylamide comonomers include N—C₁₋₁₂ alkylacrylamides or methacrylamides, such as N-butyl and N-octyl acrylamideor methacrylamide. Suitable acidic comonomers for the amphotericpolymers are those having at least one available carboxylic acid group.These include acrylic acid, methacrylic acid, crotonic acid, itaconicacid, maleic acid, fumaric acid and the C₁-C₄ alkyl half esters ofmaleic and fumaric acids, such as methyl hydrogen maleate and butylhydrogen fumarate as well as any other acidic monomers which are capableof being copolymerized with the particular copolymer system. Theamphoteric polymer may also be derived from C₁₋₁₂ alkyl, hydroxyalkyl orN-alkyl acrylates or methacrylates; diacetone acrylamide; vinyl esters,e.g., vinyl acetate; and styrene monomers such as styrene andalpha-methyl stryrene.

Suitable comonomers which form the structural unit of the carboxylcontaining copolymer binder include styrene and unsaturated carboxylicacids and their derivatives, such as (meth) acrylic acid and (meth)acrylates. The comonomers include methylethyl butyl, 2-hydroxyethylacrylate and methacrylate.

The unsaturated monomer in the first layer include acrylate andmethacrylate derivatives of alcohols, isocyanate, esters, epoxides andthe like. Examples are diethylene glycol diacrylate, trimethyolpropanetriacrylate, pentaerythritol triacrylate, polyoxyethylated andpolyoxypropylated trimethyolpropane triacrylate and trimethacrylate, andsimilar compounds as disclosed in U.S. Pat. No. 3,380,831,di-(3-methacryloxy-2-hydroxypropyl) ether of tetrachloro bisphenol-A,di-(2-methacryloxyethyl) ether of tetrachloro bisphenol-A,di-(3-methacryloxy-2-hydroxypropyl) ether of tetrabromobisphenol- A,di(2-methacryloxyethyl) ether of tetrabromo-bisphenol-A,triethyleneglycol dimethacrylate, trimethylol propane triacrylate,polycaprolactone diacrylate, and aliphatic and aromatic urethaneoligomeric di(meth) acrylates from Sartomer, West Chester, Pa. andEbecryl® 6700 available from UCB Chemicals, Smyrna, Ga.

The second layer of the photoimageable coating is derived from (i) acobinder, (ii) an acrylated urethane, (iii) a photoinitiator and (iv) ablocked polyisocyanate. The cobinder is derived from .a low molecularweigh copolymer having a molecular weight from 3,000 to 15,000 and ahigh molecular weight copolymer having a molecular weight from 40,000 to500,000.

The low molecular weight copolymer is derived from a unsaturatedcarboxylic acid or precursor and a comonomer. Examples of suitableethylenically unsaturated carboxylic acid or carboxylic acid precursorcomonomers include acrylic and methacrylic acids; maleic acid; maleicacid half ester or anhydride; itaconic acid; itaconic acid half ester oranhydride; citraconic acid; citraconic acid half ester or anhydride; andsubstituted analogues thereof. Suitable comonomers, which form the lowmolecular weight copolymer binder include styrene, substituted styrenes,and unsaturated carboxylic acid derivatives, such as, for example,esters and amides of acrylic and methacrylic acids. Methyl methacrylate,ethyl methacrylate, butyl methacrylate, methacrylamide, methyl acrylate,ethyl acrylate, butyl acrylate, acrylamide, hydroxethyl acrylate,hydroxyethyl methacrylate and styrene are preferred.

Suitable high molecular weight copolymer cobinders, which are used incombination with the low molecular weight carboxylic acid containingcopolymer binder component, are formed from the same components as thelow molecular weight copolymer.

The acrylated urethane is generally a urethane diacrylate which is thereaction product of toluene diisocyanate with a polyol with the endisocyanate groups end-capped with hydroxyethyl acrylate. The acrylatedurethane may also include diacrylates and triacrylates which arecarboxylated to provide acid numbers ranging from 1 to 50 or more andmolecular weights ranging from 500 to 5000. Carboxylated urethanediacrylates and triacrylates are particularly advantageous since theyprovide cleaner development in aqueous basic developer.

Both layers of the coating use a photoinitiator or photoinitiatorsystem. Numerous conventional photoinitiator systems are known to thoseskilled in the art and may be used herein provided they are compatiblewith the other ingredients of the coating composition.

The second layer of the photoimageable coating is a blockedpolyisocyanate crosslinking agent. The crosslinking agent includes thoseblocked polyisocyanates or mixtures of polyisocyanates which have acleavage temperature of at least 100° C. Particularly preferred blockedpolyisocyanates are methylethyl ketoxime blocked 1,6-diisocyanatohexanetrimers and methylethyl ketoxime blocked isophorone diisocyanate.

Copper Oxide Layer

In another embodiment, the copper or copper alloy substrate is treatedto form a copper oxide layer on the surface of the substrate. The copperoxide is formed by treating the copper or copper alloy substrate with anaqueous oxidizing composition. The oxidizing compositions may includeoxidzing agents such as sodium chlorite, potassium persulfate, potassiumchlorate, potassium perchlorate, etc. The oxidzing solution is appliedby dipping, , spraying or the like. The oxidzing compositions andmethods of application are described in U.S. Pat. No. 4,902,551, issuedto Nakaso et al, which is hereby incorporated by reference.

Reduced Copper Oxide Layer

In another embodiment, a reduced copper oxide layer is formed on thecopper or copper alloy substrate. The reduced copper oxide layer isformed with an aqueous aldehyde solution while applying a potential tothe copper oxide layer; after contacting a metal piece made of coppermetal or a metal nobler than copper, or after contacting with an aqueoussolution of alkali borohydride. The aldehyde may be formaldehyde,paraformaldehyde or benzaldehyde. The compositions and methods formaking the reduced copper oxide layer are described in U.S. Pat. No.4,902,551, issued to Nakaso et al, which is hereby incorporated byreference.

EXAMPLES

For the following examples aqueous etching solutions, aqueous coatingsolutions, aqueous mixtures of etchant and coating solution, and aqueousstripping solutions were used as described in accompanying tables. Theaqueous etching solutions were prepared using 30.5% sulfuric acid, 5.7%thiourea, 30 g/l wet copper thiourea sulfate crystals, saturated oxygen,saturated helium, 1% saturated iodine solution, 1% sodium hypochlorite,2.5% cobalt oxide, 5% 0.2N BriBrO₃ solution, 5% ferric chloride, 10%methane sulfonic acid (70% MSA), 5.7%1-methyl-3-propyl-imidazole-2-thione (PTI), 5% copper thiourea methanesulfonate complex, 5% copper PTI sulfuric acid complex.

TABLE 1 Etching solutions: Etchant Composition: E1 Sulfuric acid,thiourea, copper thiourea sulfate, dissolved oxygen E2 Sulfuric acid,thiourea, copper thiourea sulfate, iodine E3 Sulfuric acid, thiourea,copper thiourea sulfate, sodium hypochlorite E4 Sulfuric acid, thiourea,copper thiourea sulfate, cobalt oxide E5 Sulfuric acid, thiourea, copperthiourea sulfate, Br⁻/BrO₃ E6 Sulfuric acid, thiourea, copper thioureasulfate, ferric chloride E7 Methane sulfonic acid, thiourea, copperthiourea methane sulfonate complex, dissolved oxygen E8 Sulfuric acid,PTI, copper PTI sulfuric acid complex, dissolved oxygen Com- Sulfuricacid, thiourea, dissolved par- oxygen ative E1 Com- Sulfuric acid,thiourea, copper par- thiourea sulfate, saturated with ative helium gasE2

The aqueous coating solutions are described in table 2.

C-1 C-2 C-3 C-4 C-5 Stannous Methane  6 g/l 27 g/l 10 g/l 10 g/l 10 g/lSulfonate Bismuth Methane — — —  2 g/l — Sulfonate Indium methanesulfonate — — — —  1 g/l Sulfuric Acid 10% — 10% — — Methane sulfonicacid —  6% — 10% 10% Citric acid — 28% — — — Urea 40 g/l — — — —Thiourea  6 g/l 10 g/l — 60 g/l 60 g/l PTI¹ — — 60 g/l — — 1 =1-methyl-3-propyl-imidazole-2-thione

The aqueous mixtures of etching and coating solution are described intable 3.

M-1 M-2 M-3 M-4 Sulfuric Acid 10% 10% 10% — Methane sulfonic acid — — — 6% Citric acid — — — 28% Urea 40 g/l 40 g/l — — Thiourea  6 g/l  6 g/l— 10 g/l PTI¹ — — 60 g/l — Copper thiourea sulfate  6 g/l  4 g/l CopperPTI¹ sulfate  4 g/l Copper thiourea methane  5 g/l sulfonate StannousMethane Sulfonate  6 g/l  6 g/l 10 g/l 27 g/l Bismuth Methane Sulfonate— — — — Indium methane sulfonate — — — — 1 =1-methyl-3-propyl-imidazole-2-thione

Stripping solutions were used as described in table 4.

TABLE 4 Stripping Solutions: Stripper Description S1 McGean-RohcoRostrip M-20 S2 McGean-Rohco Rostrip M-50

Example 1

A solution of E1 was sprayed for 60 seconds at 100° F. onto aconventional copper surface using the single jet method. Examination bySEM showed that the surface had numerous shallow depressions or cups. Inother words, the surface was non uniformly etched. The number ofdepressions was much greater near the impingement zone and in the walljet region (<5 mm from impingement) than in other regions.

Example 2

A solution of E1 was sprayed for 60 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof C1 was sprayed onto the surface for 60 seconds at room temperature.The resulting panel had white/shiny color associated with a successfulapplication of immersion tin. Examination by SEM showed that the surfacewas similar to example 2 (non uniformly etched).

Example 3

A solution of E1 was sprayed for 10 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof C1 was sprayed onto the surface for 10 seconds at room temperature.This cycle was repeated eight times. The resulting panel had white/shinycolor associated with a successful application of immersion tin.Examination by SEM showed that the surface contained numerous pores lessthan 10 microns in diameter. The pores were interconnected. The quantityof pores was greater near the impingement zone and the wall jet regionthan in other regions.

Example 4

A solution of E1 was sprayed for 10 seconds at 100° F. onto a reversetreated copper surface using the single jet method. Then a solution ofC1 was sprayed onto the surface for 10 seconds at room temperature. Thiscycle was repeated eight times. The resulting panel had white/shinycolor associated with a successful application of immersion tin.Examination by SEM showed that the surface contained numerous pores lessthan 10 microns in diameter. The quantity of pores was greater near theimpingement zone and the wall jet region than in other regions greaterthan 5 mm from the impingement point. Also, the pores seemed to be morenumerous near the ‘tops’ of the MLS protrusions near the impingementzone and the wall jet region. In the zones greater than 5 mm from theimpingement point the pores tended to be more numerous near the base ofthe protrusions.

Example 5

A solution of E2 was sprayed for 10 seconds at 100° F. onto a reversetreated copper surface using the single jet method. Then a solution ofC1 was sprayed onto the surface for 10 seconds at room temperature. Thiscycle was repeated eight times. The resulting panel had white/shinycolor associated with a successful application of immersion tin. Thepanel was then immersed into a solution of S1 for 120 seconds. Thewhite/shiny color was no longer present and a deep rich copper color waspresent. Examination by SEM showed that the surface contained numerouspores less than 10 microns in diameter. The quantity of pores wasgreater near the impingement zone and the wall jet region than in otherregions greater than 5 mm from the impingement point. Also, the poresseemed to be more numerous near the ‘tops’ of the MLS protrusions nearthe impingement zone and the wall jet region. In the zones greater than5 mm from the impingement point the pores tended to be more numerousnear the base of the protrusions. Energy dispersive x-ray analysis ofthe surface showed that the tin concentration near the surface wasundetectable.

Example 6

A solution of E3 was sprayed for 10 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof Cl was sprayed onto the surface for 10 seconds at room temperature.This cycle was repeated eight times. The resulting panel had white/shinycolor associated with a successful application of immersion tin.Examination by SEM showed that the surface contained numerous pores lessthan 10 microns in diameter. The pores were interconnected. The quantityof pores was greater near the impingement zone and the wall jet regionthan in other regions.

Example 7

A solution of E4 was sprayed for 10 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof C1 was sprayed onto the surface for 10 seconds at room temperature.This cycle was repeated eight times. The resulting panel had white/shinycolor associated with a successful application of immersion tin.Examination by SEM showed that the surface contained numerous pores lessthan 10 microns in diameter. The pores were interconnected. The quantityof pores was greater near the impingement zone and the wall jet regionthan in other regions.

Example 8

A solution of E5 was sprayed for 10 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof C1 was sprayed onto the surface for 10 seconds at room temperature.This cycle was repeated eight times. The resulting panel had white/shinycolor associated with a successful application of immersion tin.Examination by SEM showed that the surface contained numerous pores lessthan 10 microns in diameter. The pores were interconnected. The quantityof pores was greater near the impingement zone and the wall jet regionthan in other regions.

Example 9

A solution of E6 was sprayed for 10 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof C1 was sprayed onto the surface for 10 seconds at room temperature.This cycle was repeated eight times. The resulting panel had white/shinycolor associated with a successful application of immersion tin.Examination by SEM showed that the surface contained numerous pores lessthan 10 microns in diameter. The pores were interconnected. The quantityof pores was greater near the impingement zone and the wall jet regionthan in other regions

Example 10

A solution of E7 was sprayed for 10 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof C2 was sprayed onto the surface for 10 seconds at room temperature.This cycle was repeated eight times. The resulting panel had white/shinycolor associated with a successful application of immersion tin.Examination by SEM showed that the surface contained numerous pores lessthan 10 microns in diameter. The pores were interconnected. The quantityof pores was greater near the impingement zone and the wall jet regionthan in other regions.

Example 11

A solution of E8 was sprayed for 10 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof C3 was sprayed onto the surface for 10 seconds at room temperature.This cycle was repeated eight times. The resulting panel had white/shinycolor associated with a successful application of immersion tin.Examination by SEM showed that the surface contained numerous pores lessthan 10 microns in diameter. The pores were interconnected. The quantityof pores was greater near the impingement zone and the wall jet regionthan in other regions.

Example 12

A solution of E1 was sprayed for 10 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof C4 was sprayed onto the surface for 10 seconds at room temperature.This cycle was repeated eight times. The resulting panel had white colorassociated with a successful application of immersion tin/bismuth alloy.Examination by SEM showed that the surface contained numerous pores lessthan 10 microns in diameter. The pores were interconnected. The quantityof pores was greater near the impingement zone and the wall jet regionthan in other regions.

Example 13

A solution of E1 was sprayed for 10 seconds at 100° F. onto aconventional copper surface using the single jet method. Then a solutionof C5 was sprayed onto the surface for 10 seconds at room temperature.This cycle was repeated eight times. The resulting panel had the offwhite color associated with a successful application of immersiontin/indium alloy. Examination by SEM showed that the surface containednumerous pores less than 10 microns in diameter. The pores wereinterconnected. The quantity of pores was greater near the impingementzone and the wall jet region than in other regions.

Example 14

A solution of E1 was sprayed for 10 seconds at 100° F. onto a brass HullCell surface using the single jet method. Then a solution of C1 wassprayed onto the surface for 10 seconds at room temperature. This cyclewas repeated eight times. The resulting panel had white/shiny colorassociated with a successful application of immersion tin. Examinationby SEM showed that the surface contained numerous pores less than 10microns in diameter. The pores were interconnected. The quantity ofpores was greater near the impingement zone and the wall jet region thanin other regions.

Example 15

RTF copper foil, after cleaning in a dilute solution of sodium hydroxideat 100° F., cold water rinsing, etching for 10 seconds in a solution of5% H₂SO₄ and 2% of 35% H₂O₂ and cold water rinsing was immersed into asolution of M1 at 110° F. containing 6 g/l Cu as copper thiourea sulfateand sparged with compressed air for 60 seconds. The resulting foil hadthe white/shiny color associated with a successful application ofimmersion tin. Examination by SEM showed that the surface had a fewpores less than 10 microns in diameter usually greater in number towardthe top of the MLS protrusions but had also produced large scallopedridges near the base of the RTF protrusions.

Example 16

RTF copper foil, after cleaning in a dilute solution of sodium hydroxideat 100° F., cold water rinsing, etching for 10 seconds in a solution of5% H₂SO₄ and 2% of 35% H₂O₂ and cold water rinsing was immersed into asolution of M2 at 110° F. containing 6 g/l Cu as copper thiourea sulfateand sparged with helium for 60 seconds. The resulting foil had thewhite/shiny color associated with a successful application of immersiontin. Examination by SEM showed that the surface had essentially nopores.

Example 17

Using the single jet apparatus M1 at a temperature of 110° F. and with acopper thiourea sulfate concentration of 6 g/l as Cu was sprayed ontothe surface of a conventional copper foil for 60 seconds. The resultingfoil had the white/shiny color associated with a successful applicationof immersion tin. Examination by SEM showed that the surface containednumerous pores less than 10 microns in diameter. The pores wereinterconnected. The quantity of pores was greater near the impingementzone and the wall jet region than in other regions.

Example 18

Using the single jet apparatus M2 at a temperature of 110° F. and with acopper thiourea sulfate concentration of 6 g/l as Cu was sprayed ontothe surface of a conventional copper foil for 60 seconds. The resultingfoil had the white/shiny color associated with a successful applicationof immersion tin. Examination by SEM showed that the surface containedno pores.

Example 19

Using the single jet apparatus M3 at a temperature of 110° F. and with acopper PTI sulfate concentration of 4 g/l as Cu was sprayed onto thesurface of a conventional copper foil for 60 seconds. The resulting foilhad the white/shiny color associated with a successful application ofimmersion tin. Examination by SEM showed that the surface containednumerous pores less than 10 microns in diameter. The pores wereinterconnected. The quantity of pores was greater near the impingementzone and the wall jet region than in other regions.

Example 20

Using the single jet apparatus M4 at a temperature of 110° F. and with acopper thiourea MSA concentration of 5 g/l as Cu was sprayed onto thesurface of a conventional copper foil for 60 seconds. The resulting foilhad the white/shiny color associated with a successful application ofimmersion tin. Examination by SEM showed that the surface containednumerous pores less than 10 microns in diameter. The pores wereinterconnected. The quantity of pores was greater near the impingementzone and the wall jet region than in other regions.

Example 21

Using the conveyorized spray line apparatus M1 at a temperature of 100°F. and with a copper thiourea sulfate concentration of 6 g/l as Cu wassprayed onto the surface of a reverse treated copper foil for 30 secondsdwell time. The resulting foil had the white/shiny color associated witha successful application of immersion tin. Examination by SEM showedthat the surface contained abundant pores which were interconnected andin general had diameters less than 10 microns.

Example 22

Using the conveyorized spray line apparatus M1 at a temperature of 120°F. and with a copper thiourea sulfate concentration of 6 g/l as Cu wassprayed onto the surface of a reverse treated copper foil for 30 secondsdwell time. The resulting foil had the white/shiny color associated witha successful application of immersion tin. Examination by SEM showedthat the surface was covered in pores which were interconnected and ingeneral had diameters less than 10 microns.

Example 23

Using the conveyorized spray line apparatus M1 at a temperature of 120°F. and with a copper thiourea sulfate concentration of 6 g/l as Cu wassprayed onto the surface of a reverse treated foil for 15 seconds dwelltime. The resulting foil had the white/shiny color associated with asuccessful application of immersion tin. Examination by SEM showed thatthe surface had very few pores which were interconnected and in generalhad diameters less than 10 microns.

Example 24

Using the conveyorized spray line apparatus M1 at a temperature of 120°F. and with a copper thiourea sulfate concentration of 6 g/l as Cu wassprayed onto the surface of a reverse treated foil for 45 seconds dwelltime. The resulting foil had the white/shiny color associated with asuccessful application of immersion tin. Examination by SEM showed thatthe surface was covered in pores which were interconnected and ingeneral had diameters less than 10 microns and that the peaks of the RTFprotrusions had been ‘eroded’ away in the process.

The following are comparative examples. The examples lack one or more ofeither an oxidizing agent or copper complex.

Comparative Example A

A solution of Comparative Example 1 was sprayed for 60 seconds at roomtemperature onto a conventional copper surface using the single jetmethod. Examination by SEM showed that the surface was uniformly etched.

Comparative Example B

A solution of Comparative E2 was sprayed for 60 seconds at 100° F. ontoa conventional copper surface using the single jet method. Examinationby SEM showed that the surface was uniformly etched.

Comparative Example C

A solution of Comparative E2 was sprayed for 10 seconds at 100° F. ontoa reverse treated copper surface using the single jet method. Then asolution of C1 was sprayed onto the surface for 10 seconds at roomtemperature. This cycle was repeated eight times. The resulting panelhad white/shiny color associated with a successful application ofimmersion tin. Examination by SEM showed that the surface did not havepores.

Comparative Example D

RTF copper foil, after cleaning in a dilute solution of sodium hydroxideat 100° F., cold water rinsing, etching for 10 seconds in a solution of5% H₂SO₄ and 2% of 35% H₂O₂ and cold water rinsing was immersed into asolution of M1 without any copper thiourea sulfate at 110° F. andsparged with compressed air for 60 seconds. The resulting foil had thewhite/shiny color associated with a successful application of immersiontin. Examination by SEM showed that the surface was not porous.

Comparative Example E

Using the single jet apparatus Ml at a temperature of 110° F. and with acopper thiourea sulfate concentration of 0 g/l as Cu was sprayed ontothe surface of a conventional copper foil for 60 seconds. The resultingfoil had the white/shiny color associated with a successful applicationof immersion tin. Examination by SEM showed that the surface hadessentially no pores.

Comparative Example F

Using the conveyorized spray line apparatus M1 at a temperature of 110°F. and with a copper thiourea sulfate concentration of 0 g/l as Cu wassprayed onto the surface of a conventional copper foil for 30 secondsdwell time. The resulting foil had the white/shiny color associated witha successful application of immersion tin. Examination by SEM showedthat the surface had essentially no pores.

Comparative Example G

Using the conveyorized spray line apparatus M1 at a temperature of 75°F. and with a copper thiourea sulfate concentration of 6 g/l as Cu wassprayed onto the surface of a conventional copper foil for 30 secondsdwell time. The resulting foil had the white/shiny color associated witha successful application of immersion tin. Examination by SEM showedthat the surface contained very few pores.

Example 25

Reverse treated copper laminate Polyclad laminates, Inc., Franklin, N.H.was prepared using the method outlined in Example 22 and then posttreated using McGean-Rohco 776PT, then laid up to make a five layermultilayer board using techniques well understood by those in theindustry. A similar multilayer board was prepared using the methodoutlined in Comparative Example F. Coupons from these two boards werethen simultaneously immersed into molten solder at various temperaturesand the times to delamination compared. The coupons which were made fromporous laminate exceeded the times to delamination of the coupons madefrom non porous laminate as described in Table 5.

TABLE 5 % increase in time to delamination of a 5 layer Temperature ofmultilayer board with channels vs. similar board molten solder withoutchannels 450° F. 125% 475° F. 160% 500° F. 250% 550° F. 400%

Example 26

Using both conventional and reverse treated copper laminate treatmentsof the surface using the methods outlined in Examples 15 and 16 andComparative Example G were performed. The resulting laminates were madeinto 5 layer McGean-Rohco 776 PT treated printed wiring boards asdescribed in Example 32 and cut into coupons. These coupons were thenexposed to 85° C/85% relative humidity for 72 hours, subsequentlyallowed to sit for 24 hours at room temperature, then immersed in moltensolder at 288° C. The results of these tests are presented in Table 6.

TABLE 6 Time to Delamination in 288° C. Molten Solder Following Exposureto 85° C./85% relative humidity for 72 hours: Amount of interconnectedchannels less Treatment than 10μ in Conventional Reverse Treated method:diameter Copper Laminate Copper Laminate Comparative none 40 seconds 45seconds Example H Example 15 many 45 seconds 50 seconds Example 16entire surface 75 seconds 75 seconds

As can be seen from Table 6, the methods of the present inventionprovide pores which form interconnected channels on the copper or copperalloy substrate.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

What is claimed is:
 1. A method of producing a substrate which includespreparing a surface capable of making a cocontinuous bond comprising thesteps of 1) obtaining a copper or copper alloy substrate and 2) applyingan etching composition which comprises (a) an acid, (b) an oxidizingagent, (c) a copper complexing agent selected from the group consistingof thioureas and imidazole-thiones, and (d) a copper complex, whereinthe copper complex is present in an amount which precipitates whenapplied to the copper or copper alloy substrate.
 2. The method of claim1 wherein the etching composition is applied by spraying.
 3. The methodof claim 1 wherein the etching composition is applied by immersing thesubstrate in the etching composition.
 4. The method of claim 1 furthercomprising the step of 3) treating the substrate with a coatingcomposition.
 5. The method of claim 4 wherein the coating composition isan immersion metal coating composition.
 6. The method of claim 5 whereinthe metal of the immersion metal coating composition is selected fromthe group consisting of bismuth, gallium, germanium, gold, indium, lead,palladium, silver, tin and alloys of said meals.
 7. The method of claim4 wherein steps 2 and 3 are repeated, sequentially.
 8. The method ofclaim 4 wherein steps 2 and 3 are repeated at least 4 times,sequentially.
 9. The method of claim 4 further comprising the step of 4)applying a stripping composition to the substrate.
 10. The method ofclaim 1 wherein a coating composition is applied to the substratesimultaneously with the etching composition.
 11. A method of producing asubstrate which includes preparing a surface capable of making acocontinuous bond comprising the steps of: 1) obtaining a copper orcopper alloy substrate; 2) applying an etching composition whichcomprises (a) an acid, (b) an oxidizing agent, (c) a copper complexingagent and (d) a copper complex; and 3) treating the substrate with acoating composition; wherein the copper complex is present in an amountwhich precipitates when applied to the copper or copper alloy substrateand wherein the coating composition is an immersion metal coatingcomposition.
 12. The method of claim 11 wherein the metal of theimmersion. metal coating composition is selected from the groupconsisting of bismuth, gallium, germanium, gold, indium, lead,palladium, silver, tin and alloys of said metals.
 13. A method ofproducing a substrate which includes preparing a surface capable ofmaking a cocontinuous bond comprising the steps of: 1) obtaining acopper or copper alloy substrate; 2) applying an etching compositionwhich comprises (a) an acid, Cb) an oxidizing agent, (c) a coppercomplexing agent and (d) a copper complex; and 3) treating the substratewith a coating composition; wherein the copper complex is present in anamount which precipitates when applied to the copper or copper alloysubstrate and wherein steps 2 and 3 are repeated sequentially.
 14. Amethod of producing a substrate which includes preparing a surfacecapable of making a cocontinuous bond comprising the steps of: 1 )obtaining a copper or copper alloy substrate; 2) applying an etchingcomposition which comprises (a) an acid, (b) an oxidizing agent, (c) acopper complexing agent and (d) a copper complex; 3) treating thesubstrate with a coating composition; wherein the copper complex ispresent in an amount which precipitates when applied to the copper orcopper alloy substrate and wherein steps 2 and 3 are repeated at least 4times sequentially.
 15. A method of producing a substrate which includespreparing a surface capable of making a cocontinuous bond comprising thesteps of: 1) obtaining a copper or copper alloy substrate; 2) applyingan etching composition which comprises (a) an acid, (b) an oxidizingagent, (c) a copper complexing agent and (d) a copper complex; 3)treating the substrate with a coating composition; and 4) applying astripping composition to the substrate; wherein the copper complex ispresent in an amount which precipitates when applied to the copper orcopper alloy substrate.
 16. A method of producing a substrate whichincludes preparing a surface capable of making a cocontinuous bondcomprising the steps of: 1) obtaining a copper or copper alloysubstrate; and 2) applying an etching composition which comprises (a) anacid, (b) an oxidizing agent, (c) a copper complexing agent and (d) acopper complex; wherein the copper complex is present in an amount whichprecipitates when applied to the copper or copper alloy substrate andwherein a coating composition is applied to the substrate simultaneouslywith the etching composition.